(1) Field of the Invention
The present invention relates to a communication device for communicating between a rotary assembly and a non-rotary assembly, to an aircraft rotor fitted with the communication device, and to an aircraft fitted with the rotor.
(2) Description of Related Art
The invention thus lies in the technical field of means for transmitting data between equipment located in a stationary frame of reference and equipment located in a moving frame of reference. The data may be defined in a digital format.
Transmission must be reliable and advantageously should not give rise to any significant disturbances such as electrical disturbances. These characteristics are looked for in particular in an application restricted to the field of aviation which is particularly constraining and demanding.
Electrical connector devices comprising slip rings and brushes are known, having a non-rotary portion and a rotary portion that are connected together by the brushes. By way of example, the non-rotary portion has circular electrically-conductive tracks and the rotary portion has respective brushes traveling over each of the tracks.
In a rotary wing aircraft, the non-rotary portion may power a plurality of heater mats present on the blades of the rotary wing, and it may power them in application of a sequence that is programmed in the electrical unit for the purpose of de-icing or of preventing ice from forming on the blades. Each mat is then connected by an electric cable to a brush of the rotary portion of the slip-ring assembly.
Such a slip-ring assembly is heavy, in particular because of the large number of electrical cables and of electric tracks.
The slip-ring assembly is thus easy to install on a heavy rotorcraft with a powerful power plant. However, installing it on a medium weight rotorcraft can be difficult.
It also appears to be difficult to install such a slip-ring assembly in temporary manner, e.g. for the purpose of performing spot tests on a rotorcraft over a limited period of time.
In addition, the friction between each brush and the corresponding track tends to degrade the performance of the slip-ring assembly. Such wear can give rise to noise that interferes with the signals being transmitted. Maintenance actions requiring the assembly to be disassembled therefore need to be performed relatively frequently. Unfortunately, a slip-ring assembly is sometimes difficult to access, so the cost of maintenance can be high and leads to the rotorcraft being out of operation for a long time.
A slip-ring assembly can have only a limited number of data inputs and thus of data outputs.
Document US 2010/0216398 describes a rotorcraft, the rotorcraft having a rotor mast supporting and driving a hub of a rotor of the rotorcraft.
The rotorcraft includes a communication device having a movable communication module and a stationary communication module. The rotor mast also has a hollow shaft forming part of the communication device.
An antenna of the movable communication module communicates with an antenna of the stationary communication module, at least in part via the rotor mast.
That communication device is advantageous. Nevertheless, it clearly presents the drawback of using the mast of a rotor. Under such circumstances, incorporating it in an already-existing aircraft can naturally be difficult.
Wireless data transmission devices are also known, in particular devices that use optical means.
Document U.S. Pat. No. 4,625,256 belongs to a technical field remote from the invention. That document describes a spark-gap for protecting a mechanical assembly from an electric current generated by lightning.
The following documents are also known: U.S. Pat. Nos. 5,205,710; 4,026,660; and US 2010/216398.